Question for all the cam gurus ... For a high RPM 2.0L 4G63 - ooh, say 9500 rpm redline with frequent use to between 9200-9300 rpm in a road racing scenario - would it be preferable to go with a lower lift, higher duration cam, or can I use a higher lift cam without worrying about my valvetrain?

Specifically - I am starting to map out an upgrade path to an HTA3582R turbo from my current 50 trim, which, to get full use out of the 35R, would require me pushing the engine further than I currently am. With that change, I am debating whether it would be worth it to upgrade from my current set of HKS280 cams to something like a Kelford 272 or perhaps even an FP5R. I have an AMS ported head with the AMS supertech springs, etc.

Really the question is, how do I prioritize:
- lift
- duration
- ramp rate
for high rpm use?

l8r)

 

I don't really qualify as a guru but i can give you my personal opinion.


Something in the 272-280 duration would get you into the rpm range you want. I personally think a cam with moderate to high lift say somewhere between 10.5-11mm and then to give it the power big ramp rates.

The ramp rate should give you a better effective duration allowing for more power. The Kelford 272 cams are like this same with Jun and others.

 

The Kelfords will spool a little faster and should deliver a bit more power on account of their more aggressive ramp rates.

Power cannot be made without accurate valvetrain actuation. Accurate valvetrain actuation cannot be achieved with insufficient spring rates. Sufficient spring rates are a function of cam lobe profiles and rpm, whereas the more aggressive the lobe profile, or the greater the rpm, the greater the required spring rates.

If you already have the valvetrain, you may as well have the cams to utilize it.

 

So no concerns with a higher lift cam causing excessive wear on the valvetrain with prolonged high RPM use? Or is it something that I'll just have to start adding to the maintenance cycle ... i.e., something like inspect the valvetrain annually, or after 'x' track events.

l8r)

... thanks for chiming in.

 

Naturally higher lift, nasty ramp rates and higher rpm contribute to faster wear rates for parts like valve guides, but with your first words referring to 9200-9300 rpm, I'd say you have other, potentially larger concerns than rates of valvetrain wear.

 

Yeah, I know. Although it's been holding up fine at it's current cutoff of 9100 (shift points around 8500), I realize that pushing it by another 5-700 RPM is getting into a range that 4G63's weren't really meant to be in. It would just really bug me to not use the turbo on my car to its fullest potential. From day 1 I made the decision to stick with the 2.0 and build a high-rpm 4g63 and I'm going to continue on that path, although if I had to do it over, I'd probably go the 2.3l route. The internals' capability of handling the added RPM is a big part of the decision I have to make. The cam question is really secondary, I just wanted to make sure that it would be a lesser issue than oiling, pistons, rods, heat, etc. If I can manage to scrape the cash together, I'll have to sit down and have a long talk with AMS and hopefully look at the long-term data they've collected from their various builds.

Sad to see how fast I can get used to 420 whp.

l8r)

 

I am not trying to discourage you but revving high is quite a wear and tear on everything in the engine. I mean at 9k your crank is spinning at 150 rpms a second. According to Corky Bell author of Maximum Boost just going from 6 to 7 causes and additional 144% load on the rods. IMHO its not worth it to go that high. You want to revv high i say get a bridgeported 20b lol. But that is just my opinion.

 

Have you considered going to a TS 82R as opposed to just doing the undivided housing? If a TS housing can get the 35 into the fat part of its compressor map earlier...then maybe you could keep the shift points a tad lower on your track setup.

EDIT: Me on a RR car I wouldn't wanna rev that high w/o a dry sump oiling system!

 

It's already seen 9000 on several track days, without any ill issues ... although I obviously don't rev it that high while I'm in a turn.

I would LOVE to run a twin-scroll setup, but I don't have that kind of money laying around. If I were building my car from scratch, I'd go with a TS 2.3L setup ... but I pretty much have to stick with what I have. Mind you, I'm not complaining, the 2.0L that AMS put together for me (even with the lowly 50 trim) is ridiculous.

l8r)